Fluid containment tanks are utilized in a multitude of industrial processes such as food and chemical manufacturing and processing, pharmaceutical manufacturing, wine preparation, material fermentation, and so on. It is often critical to ensure that the interior of the tank is free of unwanted debris and contaminants. For example, a tank that is typically filled to a certain level may exhibit a “tub ring” about its interior circumference at the level to which the tank is most often filled. Moreover, paddles, mixers, and other equipment within a tank may trap debris via a coating or other deposit. Tank inlets and outlets are also known to trap sediment or debris that may later reenter the tank contents during use.
Unwanted contaminants in the tank may negatively impact the quality of the finished product being processed or manufactured. Moreover, the failure to adequately clean the tank interior can violate regulations relevant to certain industries such as pharmaceutical processing. Thus, it is common to clean the interior of such tanks at certain intervals, e.g., after each process batch, to ensure product quality and adherence to any relevant regulations.
Tank cleaning machines and equipment are available that clean debris and residue from within tanks and other vessels through the use of what is commonly known as impingement cleaning. One common type of cleaning system employs a tool inserted into the tank. The inserted tool may be placed permanently or temporarily within the tank and is typically sealed to the tank via a flange. A rod-like extension of the tool within the tank interior supports a rotary spray head affixed at its innermost end. The rod-like extension comprises a fixed tubular housing supporting an internal rotary shaft for rotating the spray head about the axis of the shaft. In addition, the spray head is generally geared to the fixed housing such that as the spray head rotates about the axis of the shaft, it also turns upon an axis perpendicular to the shaft.
The relationship between the shaft rotation and the rotation of the spray head perpendicular to the shaft depends upon the ratio of the gearing connecting the spray head to the fixed housing. Typically, the ratio is selected such that a combination of a particular orientation and position of the spray head repeats only after multiple revolutions of the shaft. This technique staggers subsequent traces of the spray against the tank interior on each shaft revolution to ensure that substantially every portion of the tank interior is exposed to the cleaning spray at some point during the cleaning process.
While this system is simple and mechanically robust, it creates certain inefficiencies and can also be less than fully effective depending upon the mode of operation. With respect to effectiveness, it will be appreciated that known systems such as those described above are not adapted to provide a constant volume of cleaning solution against all portions of a uniformly soiled surface. Moreover, systems such as those described above are not adapted to provide a volume of cleaning solution against particular portions of the interior in relation to the known heavy soiling of those portions.
For example, in the case of a deposit ring at a vessel fill line, although the fill line portion of the interior is known to experience increased soiling, existing systems do not allow the operator to customize the clean operation to more heavily clean such portions. Thus, in typical uses, the systems described above may lead to excess cleaning of some tank portions and inadequate cleaning of other portions. Although the cleaning duration may be prolonged to ensure adequate cleaning of the most heavily soiled interior portions, this leads to additional waste of time, cleaning fluid, and energy with respect to the lightly soiled surfaces.